The Tutorial Trails 1 and 2 introduce the packages roaf.gps and roafx.gui. The GPXviewer combines these two packages to combine the components for global positioning, time keeping, and drawing of spatial data. GPX is the most commonly used (exchange) format for GPS data. This tool, with its subcomponents, should come in handy for every ROAF developer to analyze spatial data.

Note that you can find a similar project 'JavaGPS' at SourceForge with a slightly different domain (NMEA files and many different projection systems). The image of this project was used and its NMEA file demo.gpslog was converted to HDcastle.gpx format.